This invention relates to corn harvesting machinery and more particularly the corn row unit of the corn head commonly used with modern self-propelled combines. Corn heads include individual row units normally designed for harvesting a single row of crop material. To accommodate various spacings between rows of crops, these row units are usually adjustably attached to a horizontally disposed frame member. The modern trend in corn headers appears to be one of placing the row units at a low profile to the ground, closer together and providing for increasingly larger throughputs.
Each row unit contains a row crop divider, a row unit hood, gathering/conveying chain(s), two stripper plates, two stalk rolls, a row unit frame, and a gearbox. The gearbox powers the row unit for gathering corn plants then stripping, separating, and conveying ears of corn from the corn plant.
The transversely disposed power input shaft is powered by the combine and delivers rotational power to the individual row units. As can be seen in U.S. Pat. No. 3,589,110, for example, this power input shaft is commonly placed within the gearbox and continues therethrough from one gearbox to the next. To save costs, reduce complexity, and provide constant lubrication the internal gears are contained in a sealed gearbox. The slip clutch for each respective gearbox is seen affixed to a member contained within the gearbox and movable therewith. Typically the operating speed relationship of the stalk rolls and gathering chains is fixed as is the size of the external sprockets and stalk rolls.
As shown in FIG. 1, corn heads are provided with several row crop dividers for retrieving, lifting, and directing the rows of corn stalks toward their respective ear separation chambers. FIG. 2 shows a top isolated view of the row crop divider and more particularly the gathering chains and stalk rolls of the corn row unit as typically found in the prior art.
FIG. 3 shows the side view of a row unit found in the prior art. The stalk rolls are powered by a gearbox. As the stalk rolls rotate, the flutes on the stalk rolls pull the corn stalk downward. Two stripper plates located above the stalk rolls and on both sides of the corn row are spaced wide enough to allow to the corn plant to pass between them but narrow enough to retain the ear of corn which contain grain. This causes the ears of corn to be separated from the corn plant as it is pulled downward through the stripping plates. The stalk rolls continue to rotate ejecting the unwanted portions of the corn plant below the corn head thereby returning the unwanted portions to the field. The cooperative interaction of the stalk rolls, the stripping plates and the gathering chains of the row unit are defined as the ear separation chamber.
In the past 30 years four (4) external factors have impacted corn harvesting: (1) Corn stalk harvest heights have continued to increase. (2) Corn yields have doubled through improved genetics, fertilization, populations, and row spacings. (3) Genetics also improved insect resistance, which improved plant health, stalk vigor, and increase height at harvest time. (4) Harvesting machines are larger with increased horsepower, capacity, ground speed and utilize corn heads with more row units. These factors in combination require that during ear separation modern row units must: (1) Increase the rate of ear separation. (2) Ensure that the corn plant is not severed from its roots system. (3) Increase the speed at which corn stalks are ejected from the row unit. (4) Retain minimal amounts of MOTE (material other than ears) in the heterogeneous material being delivered to the combine for threshing.
Through research, operations, and testing, applicant has found that a major evolving problem in harvesting today's corn hybrids is a large build up of plant material (MOTE plus ears) in front of the cross auger during operation of the corn head. Combine operators commonly refer to this mass of material as “trash”, “muskrat huts”, “hair ball”, or simply “a pile of fluff”. The accumulation of MOTE reduces the efficiency of the corn head. Many times operators claim this accumulation of trash or fluff will occur during the best operating times of the day. This is especially the case when the corn is extremely dry as may be found on fall afternoons with low humidity. The appearance of this fluff or trash may be severe enough to require harvesting equipment to shut down.
During field testing, several kill stop examinations of this large pile of trash confirmed that it is composed of long pieces or the top portion of the corn plant, which had been sheared off or broken off by the gathering chain paddles. When harvesting down corn it was also noticed that root balls were unnecessarily being pulled out of the ground and dragged into the corn head due to excessive gathering chain speed.
Previous to this invention, the prior art in this field has taught that to increase row unit capacity, travel speeds and reduce trash intake the gathering chain speed should be increased. U.S. Pat. No. 3,462,928 ('928) teaches a dependent drive system employing an eight (8) tooth gathering chain drive sprocket. As taught by '928, the gear means within the gear housing drives not only the stalk rolls but also the endless gathering chains. Based on applicant's experience, this (8) tooth gathering chain sprocket appears to be the predominate size still in use with John Deere dependent drive systems.
U.S. Pat. No. 5,921,070 issued to Chamberlain (“Chamberlain”) teaches that the optimum gathering belt speed is approximately equal to the ground speed of the harvester. If the ground speed of the harvester needs to be decreased due to crop or environmental conditions, the gathering belt speed must be decreased. According to Chamberlain to meet this challenge, an independent drive system allowing independent speed control of both the gathering belts and stalk rolls is required.
There are numerous disadvantages and weaknesses in the teachings found in Chamberlain. A corn head with both variable knife and gathering belt speed requires additional elements such as motors, gearboxes and driveshafts. This increase in equipment increases the weight of the corn head and the power required to drive the head, increasing both the cost of manufacture and operation. Additionally. Chamberlain does not teach a method to convert an existing corn head having a dependent drive system. Furthermore, Chamberlain teaches that for high ground speed operations, the gathering belt speed must be higher to match the ground speed.
Field testing and experimentation by the applicant have shown that in fact reduction of gathering chain speed reduces stalk shear allowing increased ground speed operations through improved ear separation and threshing efficiencies. It has been found that when the gathering chain paddle and the corn plant enter the row unit at the same time, the stalk roll flutes are going to start pulling the corn plant downward. At the same time the gathering chain paddle is pushing the stalk up the ear separation chamber. At this point the corn stalk is simultaneously moving both laterally and vertically. If the corn stalk reaches the end of the ear separation chamber before the stalk roll consumes the majority of the corn stalk, lateral movement stops because the corn plant stalk has reached the end of the stalk rolls and is lodged against the gearbox. The gathering chain paddle then shears the upper portion of the corn stalk off with the corn plant ear attached and pushes both into the cross auger.
The problem at its most basic is that the stalk roll flutes and the gathering chain paddles are applying energy to the stalk in different directions producing a shearing effect. When the corn stalk reaches the end of the stalk rolls and stops moving horizontally, the movement of the corn stalk becomes restricted. This then allows the stalk to be sheared by the gathering chain paddle resulting in the separation of the stalk from itself. Analysis of stripper plates indicates pronounced wear at the row unit separation point. This would indicate there is significant pressure and wear at this point due to stalks separating against the stripper plate.
Additionally, field testing indicates the node below the ear may be weaker than other nodes in the stalk. The weakness in this node accentuates the tendency of the prior art to separate the stalk from itself when the stalk is subjected to shear. Recently improved agronomic technology and corn genetics have produced taller corn stalks at harvest time further highlighting this problem.